Immunohistochemical and ultrastructural study of gap junction proteins connexin26 and 43 in human arachnoid villi and meningeal tumors.

Human arachnoid villi and meningiomas are known to have gap junctions formed by connexin (Cx) proteins. We examined the expression and localization of Cxs in normal human arachnoid villi and meningeal tumors (meningiomas and hemangiopericytomas) by immunohistochemistry and Western blots. In arachnoid villi, strong immunopositivity for connexin26 (Cx26) and connexin43 (Cx43) was detected in the cap cell layer, cap cell cluster, and central core. They were weakly expressed in the fibrous capsule. In meningiomas they were strongly expressed in the meningotheliomatous area and weakly positive in the fibrous area. None of them were expressed in hemangiopericytomas. By immunoelectron microscopy, Cx26 and Cx43 were distributed on the cell membranes in arachnoid villi and meningiomas. In the Western blots in arachnoid villi and meningiomas, Cx26 and Cx43 were shown at bands with molecular weights of 26 kD and 42-47 kD, respectively. The degree of positivity for Cxs was different between subtypes of meningiomas. These findings suggest that expression of Cx26 and Cx43 might be related to the differentiation of the arachnoid villi and meningiomas, and exhibit the different origin of various subtypes of meningiomas. We proposed that Cx expression is one of the useful markers for the differentiation of meningioma and hemangiopericytoma.